Field of the Invention
This invention relates to apparatus and method for responding to an audible alarm in the presence of background noise, and more particularly to apparatus and method for audibly detecting smoke or fire alarm signals for implementing automatic telephone alert with safeguards and selective exclusions to enhance accuracy of detection.
Certain known smoke or heat detectors include inexpensive battery-operated, self-contained circuitry and apparatus that is capable of unattended operation at diverse locations around a dwelling or other structure to detect abnormal amounts of smoke or heat as an indication of a fire, and to produce a continuous loud tone intended to alert occupants of the dwelling or structure to the danger. Such self-contained devices may be positioned in numerous locations about a dwelling or structure as an add-on after construction of the structure and be dependable for sounding the tone upon detection of fire conditions. Because many such devices may be positioned around a structure, it has not been convenient to provide wire network connections to the devices, particularly in add-on installations in finished structures. In addition, these self-contained devices with limited battery power have generally not been capable of sensing fire conditions inside a structure for producing sufficiently loud tones to be audible outside the structure. Further, the warning tone produced by such devices is intended to evoke the human responses necessary to ensure personal safety and to initiate the counter measures to contain the fire danger. However, in circumstances where no humans are present within the audible range of the device inside or outside the structure, no human responses can be expected to contain the destructive effect of fire.